A gaseous light source such as heavy hydrogen, mercury, and the like are used as a deep ultraviolet light source having a light emitting wavelength of 365 nm or less. Problems of such gaseous light source are that it has short lifetime and a size of the device is large. Also, mercury is restricted from using in some cases. Therefore, a light emitting device which can solve such problems and also using a semiconductor which can be easily handled is expected.
As such deep ultraviolet light emitting device, the light emitting device using a group III nitride semiconductor represented by a compositional formula of AlqGa1-qN (0≤q≤1) is proposed. Such group III nitride semiconductor functions as the deep ultraviolet light emitting device because it is a direct bandgap type semiconductor in entire range of wavelength 200 to 365 nm (Patent Document 1 and Non-Patent Document 1).
The deep ultraviolet light emitting device using the group III nitride semiconductor device is produced in general by carrying out the crystal growth of a laminate structure made of a n-type layer, an active layer, and a p-type layer on a substrate made of single crystal. As a method of crystal growth of the semiconductor laminate structure, for example Metalorganic Chemical Vapor Deposition (MOCVD) method and Molecular Beam Epitaxy (MBE) method may be mentioned.
As the single crystal substrate used for the above crystal growth method, a foreign substrate material such as sapphire, SiC, Si, and the like, and a same substrate such as AlN, GaN, and the like are used. By carrying out the crystal growth of the semiconductor laminate structure which becomes the light emitting device on the substrate, the deep ultraviolet light emitting device using the group III nitride semiconductor is formed.